SEXUAL PHENOMENA IN THE PROTOZOA 243 



cause in the protoplasm, but in any case, it cannot be of primary 

 importance, for the one essential requisite demanded by the lowest 

 flagellate and the highest animal or plant is fusion with another cell, 

 and by such fusion the restoration of an exhausted vitality. 1 



We must finally, with Hertwig, distinguish clearly between fertili- 

 zation and reproduction. Fertilization of the ovum in Metazoa is so 

 closely followed by development of the embryo, that it has grown to 

 be considered a direct act of reproduction as well as its cause, and the 

 same view would be equally applicable to the Coccidiida or Infusoria. 

 But, when applied to conjugation in other forms of Protozoa, i.e. to 

 fertilization in its more general aspects, it is evident that the phe- 

 nomenon has some deeper significance. Biitschli ('76) long since 

 pointed out that, during the period of conjugation, the two individuals 

 of conjugating Paramcecia might have formed many others by simple 

 division, and he, with Engelmann, showed that the phenomenon, in all 

 probability, could not be a reproductive act. So, too, Onychodromus 

 might divide thirteen times during the period of conjugation (Maupas). 

 The facts of facultative conjugation, e.g. in Polytoma or in the Rhi- 

 zopoda, are arguments in the same line, for, in these cases, an individ- 

 ual may or may not fuse before forming spores. Maupas ('89) main- 

 tained that division is the only method of reproduction, and pointed 

 out that division is more rapid before conjugation than after, and 

 Hertwig ('98) showed that, in Actinosph&rium, reproduction actually 

 precedes fertilization, and he says : " A reproductive process is 

 bound up with the encystment of Actinospkcerium, whereby a mother- 

 cyst gives rise to several primary cysts, each primary cyst to a 

 germ-sphere, each germ-sphere to new individuals. Reproduction 

 here precedes fertilization, and the latter has no effect upon the former." 

 He further states that fertilization, which has no direct connection 

 with reproduction, occurs in both animals and plants, and he adds : 

 " Since we know reproduction without fertilization and fertilization 

 without reproduction, there must be processes combined in ' sexual 

 reproduction' which in their essence do not belong together. To 

 distinguish methods of increase as sexual and asexual, awakens false 

 impressions. There is, in fact, only one kind of reproduction, i.e. 

 division in the widest sense of the word. What is known as sexual 

 reproduction among Metazoa, is division which is combined with 



1 Watase's ('92) interesting suggestion as to sex-differentiation is significant in the light 

 of the foregoing facts. Regarding sex-differentiation as a manifestation of irritability (l.c., 

 p. 485), he says : " The organism is either a male or a female, not by the difference of ' primary 

 sexual characters ' alone, but by the difference which saturates the whole of its entire structure. 

 Such a difference is, however, neither absolute nor permanent. It is a temporary differenti- 

 ation of protoplasm into one of two different directions, and sooner or later comes back to 

 the original neutral or non-sexual state from which it started, thus manifesting the phenomenon 

 characteristic of all protoplasmic irritability" (p. 493). 



